ITC == Introduction To Cryptography

Pseudorandom ...

ITC == Introduction To Cryptography

Pseudorandom Number Generation And Stream Cipher

Algorithm Design

  • Purpose-built algorithms
    • 專門用來產生 pseudorandom number (bit stream)
    • 最具代表性: RC4
  • Algorithms based on existing cryptographic algorithms
    • Symmetric block ciphers
    • Asymmetric ciphers
    • Hash functions and message authentication codes

Pseudorandom Number Generators

  • Linear Congruential Generators
X_{n+1} = \left (aX_{n}+c \right ) \mod m  
  • Blum Blum Shub Generator (BBS Generator)

Pseudorandom Number Generation Using A Block Cipher

  • PRNG Using Block Cipher Modes of Operation
    • CTR Mode
      CTR Mode
    • OFB Mode
      OFB Mode

Stream Ciphers

  • A key is input to a pseudorandom bit generator that produces a stream of 8-bit numbers that are apparently random.

  • The output, called keystream, is combined one byte at a time with a plaintext stream using the bitwise XOR operation.


  • A stream cipher designed in 1987 by Ron Rivest for RSA security.



如果覺得這篇文章對你有幫助, 除了留言讓我知道外, 或許也可以考慮請我喝杯咖啡, 不論金額多寡我都會非常感激且能鼓勵我繼續寫出對你有幫助的文章。

If this blog post happens to be helpful to you, besides of leaving a reply, you may consider buy me a cup of coffee to support me. It would help me write more articles helpful to you in the future and I would really appreciate it.

Related Posts